IGCSE Chemistry 0620 Definitions and stuff to remember

proton number (atomic number)

number of protons in the nucleus of an atom

nucleon number (mass number)

total number of protons and neutrons in the nucleus of an atom

isotopes

atoms of the same element which have the same proton number but a different nucleon number

two types of isotopes

radioactive and non-radioactive

Lattice structure of ionic compounds

a regular arrangement of alternating positive and negative ions

formation of single covalent bonds in H2, Cl 2, H2O, CH4, NH3 and HCl

the sharing of pairs of electrons leading to the noble gas configuration

metallic bonding

a lattice of positive ions in a 'sea of electrons'

relative atomic mass, Ar

the average mass of naturally occurring atoms of an element on a scale where the 12C atom has a mass of exactly 12 units

relative molecular mass, Mr

the sum of the relative atomic masses

the mole

the unit representing the amount of atoms, ions, or molecules. One mole is the amount of a substance that contains 6.02 x 10^23 particles

Avogadro constant

6.02 x 10^23

electrolysis

the breakdown of an ionic compound, molten or in aqueous solution, by the passage of electricity

general principle of electrolysis

metals or hydrogen are formed at the negative electrode (cathode), and non-metals (other than hydrogen) are formed at the positive electrode (anode)

exothermic

A reaction in which energy is given out to surroundings (temperature of environment increases)

endothermic

A reaction in which energy is taken in from surroundings (temperature of environment decreases)

bond breaking

an endothermic process

bond forming

an exothermic process

effects of concentration in terms of collisions between reacting particles

an increase in concentration only causes an increase in collision rate

effects of temperature in terms of collisions between reacting particles

An increase in temperature causes an increase in collision rate and more of the colliding molecules have sufficient energy (activation energy) to react

use of silver salts in photography

process of reduction of silver ions to silver

photosynthesis

the reaction between carbon dioxide and water in the presence of chlorophyll and sunlight (energy) to produce glucose and oxygen

oxidation

gain of oxygen, loss of electrons

reduction

loss of oxygen, gain of electrons

redox

Oxidation and reduction take place together at the same time in the same reaction, electrons lost from one reactant, gained by other reactant.

oxidising agent

a substance which oxidises another substance during a redox reaction.

reducing agent

a substance which reduces another substance during a redox reaction.

acids

proton donors

bases

proton acceptors

Periodic Table

a method of classifying elements and it's used to predict properties of elements

lithium, sodium and potassium in Group I

a collection of relatively soft metals showing a trend in melting point, density and reaction with water

halogens, chlorine, bromine and iodine in Group VII

a collection of diatomic non-metals showing a trend in colour and density

transition elements

a collection of metals having high densities, high melting points and forming coloured compounds, and which, as elements and compounds, often act as catalysts. Have variable oxidation states.

noble gases, in Group VIII or 0

being unreactive, monoatomic gases because they have a complete outer shell of valent electrons.

the reactivity series

the tendency of a metal to form its positive ion

composition of clean, dry air

approximately 78% nitrogen, 21% oxygen and the remainder as being a mixture of noble gases and carbon dioxide

common pollutants in the air

carbon monoxide, sulfur dioxide, oxides of nitrogen and lead compounds

carbon monoxide sources

incomplete combustion of carbon-containing substances

sulfur dioxide sources

combustion of fossil fuels which contain sulfur compounds (leading to 'acid rain')

oxides of nitrogen sources

from car engines

lead compounds sources

leaded petrol

carbon dioxide and methane are

greenhouse gases and they trap heat within the earth's atmosphere, thus contributing to global warming

carbon dioxide sources

-a product of complete combustion of carbon-containing substances
-a product of respiration
-a product of the reaction between an acid and a carbonate
-the thermal decomposition of a carbonate

methane sources

decomposition of vegetation and waste gases from digestion in animals

uses of sulfur dioxide

a bleach in the manufacture of wood pulp for paper and as a food preservative (by killing bacteria)

uses of lime and slaked lime

treating acidic soil and neutralising acidic industrial waste products, e.g. flue gas desulfurisation

uses of calcium carbonate

manufacture of iron and cement

main constituent of natural gas

methane

petroleum

a mixture of hydrocarbons and its separation into useful fractions by fractional distillation

uses of refinery gas

bottled gas for heating and cooking

uses of gasoline fraction

fuel (petrol) in cars

uses of naphtha fraction

for making chemicals

use of kerosene/paraffin fraction

jet fuel

uses of diesel oil/gas oil

fuel for diesel engines

uses of fuel oil fraction

fuel for ships and home heating systems

uses of lubricating fraction

lubricants, waxes and polishes

use of bitumen

Making roads

homologous series

a 'family' of similar compounds with similar chemical properties due to the presence of the same functional group

properties of alkanes

generally unreactive, except in terms of burning

manufacture of alkenes and hydrogen

by cracking

manufacture of alkenes and of hydrogen

a solvent and a fuel

manufacture of ethanol

by fermentation and by the catalytic addition of steam to ethene

ethanoic acid

a typical weak acid

ester production

reaction of a carboxylic acid with an alcohol in the presence of a catalyst

polymers

large molecules built up from small units (monomers)

constituents of food

proteins and carbohydrates (polymers)

proteins

possess the same amide linkages as nylon but with different units